Trends in hospitalizations with primary varicella and herpes zoster during the prevaricella and initial postvaricella and herpes zoster vaccine eras, connecticut, 1994-2012

Background.  The introductions of the varicella vaccine in 1995 and herpes zoster (HZ) vaccine in 2006 have an ongoing potential to modify the epidemiology of both diseases. Analysis of data on hospitalizations can be conducted to examine trends in the occurrence of severe disease over time and to assess the possible impact of vaccination on the incidence of hospitalization. Methods.  Statewide hospital discharge data 1994-2012 in Connecticut were used to identify individuals discharged with a diagnosis of varicella and the initial admissions of persons with a discharge diagnosis of HZ in the first or second diagnostic position. Trends in overall age-standardized and age group-specific hospitalization rates for preselected time intervals before and after the introduction of vaccines were examined using Poisson regression models or Mantel-Haenszel χ(2) tests. Results.  Beginning in 2001, 5 years after the introduction of varicella vaccine, HZ hospitalization rates decreased significantly in individuals <15 years at an average rate of 19.4% per year through 2012. Among individuals ≥60 years, HZ hospitalization rates increased by 5.1% per year from 2001 to 2006 but decreased by 4.2% per year from 2007 to 2012. Primary varicella hospitalization rates declined 82.9% from the prevaccine era (1994-1995) to the 1-dose era (2001-2005) (P < .001). Rates further decreased significantly in the 2-dose era (2010-2012) among 5 to 9 year olds (100% decrease). Conclusions.  Varicella vaccine seems to have had an impact on both varicella and HZ hospitalizations, and introduction of the HZ vaccine may be having an impact on HZ hospitalizations.

Impact of a routine two-dose varicella vaccination program on varicella epidemiology

OBJECTIVE

One-dose varicella vaccination for children was introduced in the United States in 1995. In 2006, a second dose was recommended to further decrease varicella disease and outbreaks. We describe the impact of the 2-dose vaccination program on varicella incidence, severity, and outbreaks in 2 varicella active surveillance areas.

METHODS

We examined varicella incidence rates and disease characteristics in Antelope Valley (AV), CA, and West Philadelphia, PA, and varicella outbreak characteristics in AV during 1995-2010.

RESULTS

In 2010, varicella incidence was 0.3 cases per 1000 population in AV and 0.1 cases per 1000 population in West Philadelphia: 76% and 67% declines, respectively, since 2006 and 98% declines in both sites since 1995; incidence declined in all age groups during 2006-2010. From 2006-2010, 61.7% of case patients in both surveillance areas had been vaccinated with 1 dose of varicella vaccine and 7.5% with 2 doses. Most vaccinated case patients had <50 lesions with no statistically significant differences among 1- and 2-dose cases (62.8% and 70.3%, respectively). Varicella-related hospitalizations during 2006-2010 declined >40% compared with 2002-2005 and >85% compared with 1995-1998. Twelve varicella outbreaks occurred in AV during 2007-2010, compared with 47 during 2003-2006 and 236 during 1995-1998 (P < .01).

CONCLUSIONS

Varicella incidence, hospitalizations, and outbreaks in 2 active surveillance areas declined substantially during the first 5 years of the 2-dose varicella vaccination program. Declines in incidence across all ages, including infants who are not eligible for varicella vaccination, and adults, in whom vaccination levels are low, provide evidence of the benefit of high levels of immunity in the population.